Process for preparing thiobisphenols

ABSTRACT

A new process for the production of 4,4&#39;&#39;-mono- and/or polythiobis(2,6-dialkylphenol) is described. 2,6-Dialkylphenol reacts with sulfur powder in the presence of an alkali hydroxide or alkali metal in a solvent under heating. The process yields 4,4&#39;&#39;mono- and/or poly-thiobis(2,6-dialkylphenol) economically and in a high yield. These compounds are useful as an antioxidants.

O United States Patent [191 [111 3,835,196

Fujisawa et al. Sept. 10, 1974 PROCESS FOR PREPARING [56] References Cited THIOBISPHENOLS UNITED STATES PATENTS [75] Inventors: Tamotsu Fujisawa; Takakazu 2,207,719 7/1940 Cohen 260/608 lfo una; Kazuml Hata, all of Tokyo, OTHER PUBLICATIONS Lefevre et al., Compt. Rend. 198 1432-1434 & [73] Assignee: Sagami Chemical Research Center, 1791-1793 (1934).

Tokyo, Japan Primary Examiner-Lewis Gotts [22] Flled' 1972 Assistant Examiner-D. R. Phillips [21] Appl. No.: 304,470 Attorney, Agent, or Firm-Flynn & Frishauf Related US. Application Data TB [63] Continuation of Ser. No. 85,767, Oct. 30, 1970, [57] ABS abandonm A new process for the production of 4,4 monoand- /or poly-thiobis(2,6-dialkylphenol) is described. 2,6- [30] Foreign Applicafion Priority Data Dialkylphenol reacts with sulfur powder in the pres- N v 12 1969 Ja an 4480073 ence of an alkali hydroxide or alkali metal in a solvent 0 p under heating. The process yields 4,4'-monoand/or [52] U 8 Cl 260/608 260/609 F poly-thiobis(2,6-dialkylphenol) economically and in a [51] 49/36 149/38 high yield. These compounds are useful as an antioxi- 581 Field of Search 260/608, 609 F dams- 5 Claims, No Drawings 1 PROCESS FOR PREPARING TIIIOBISPI-IENOLS This is a continuation of application Ser. No. 85,767 filed Oct. 30, 1970, now abandoned.

BACKGROUND OF INVENTION This invention relates to a process for preparing 4,4- monoand/or poly-thiobis(2,6-dialkylphenols) having the following formula:

wherein R and R represent respectively aliphatic hydrocarbon radicals, and x is a positive integer from one to four. A method using sulfur chlorides to prepare the compounds of this series has been known heretofore. However, this prior method is not satisfactory from an industrial and economic viewpoint, because the sulfur chlorides are unstable and further, hydrochloric acid is formed as one of products and said hydrochloric acid may corrode the reaction vessel as a result.

SUMMARY OF THE INVENTION The present invention relates to a process for preparing 4,4'-monoand/or poly-thiobis(2,6-dia1kylphenol) characterized by reacting a 2,6-dialkylphenol with sulfur powder. It is advantageous to use sulfur powder directly as a starting material for sulfidation of aromatic compounds, although sulfur chlorides can be produced from sulfur powder and chlorine. The process of this invention relates to a process for preparing 4,4-monoand/or poly-thiobis(2,6-dialkylphenol) directly from a 2,6-dialkylphenol characterized by reacting 2,6- dialkylphenol withv sulfur powder in a solvent under basic condition and heating. The 2,6-dialkylphenols favored for the starting material in this invention involves hindered phenols which possess alkyl groups in 2- and 6 positions, i.e. in the positions ortho to the OH As regards the solvent which is to be used in the present process, any solvent which will not react with the basic materials or the final product may be employed. The preferred alcohols for use as solvent include methanol, ethanol, propanol, glycol and solvents such as pyridine, dimethyl formamide and dimethyl acetoamide. Also, a mixture of these solvents and water in any proportions may be used in the present invention.

In practicing the present invention, an alkali hydroxide or an alkali metal and sulfur powder is added to a hindered phenol in a solvent of the type mentioned, and is heated; the heating time is generally 0.5 50 hours. The reaction product is obtained by a conventional method from the reaction mixture after completion of the reaction.

DESCRIPTION OF PREFERRED EMBODIMENTS The following examples are not limitative, but merely illustrate this invention. In the examples all parts are by weight unless otherwise specified.

EXAMPLE 1.

A mixture of 4.1 parts of 2,6-di-t-butylphenol and 1.9 parts of sulfur powder (mole ratio 1:3) was heated under refluxing for 0.5 hour in 95 percent ethanol solution containing 1.7 parts of potassium hydroxide (1.5

group. It is important that the process of the present in hydroxide.

Molar ratio Yield (percent) r-Bu S KOH, t-Bu t-Bu @011 HO- SxQOH t-Bu t-Bu t-Bu mole g.-atom mole X=1 X=2 X--3 X=4 1 10 1.5 24 10 16 34 1 5 1.5 33 14 17 so 1 4 1.5 63 20 9 1 a 1.5 65 21 5 2 1 2 1.5 17 I 2 2 1 1 1. 5 24 4 2 2 1 0.5 1.5 a 2 1 a 0.75 31 4 6 13 1 3 2.25 62 19 6 6 vention be carried out in basic condition, and to create EXAMPLE 2.

this basic condition the use of alkali metal or alkali hydroxide is preferred. These basic materials may be used usually in the amounts of equivalent mole or more to a mole of hindered phenol.

3 EXAMPLE 3.

The procedure of Example 1 was repeated except: that 2.5 parts of 2,6-dimethylphenol were used instead of 2,6-di-t-butylphenol. By this procedure, 4,4'thiobis(2,6-dimethylphenol) (M.P. 123 4C) was isolated, the yield being 27 percent.

EXAMPLE 4.

The procedure of Example 1 was repeated except that 3.5 parts of 2,6-di-isopropylphenol were used instead of 2,6-di-t-butylphenol. By this procedure, 4,4-. monoand poly-thiobis (2,6-diisopropylphenol) was Obtained? tttq is lz in 9 PPIE F;--..

EXAMPLE 5.

The procedure of Example 1 was repeated except that 3.3 parts of 2 methyl--t-butylphenol were used instead of 2,6-di-t-butylphenol. By this procedure, 4,4-

thiobis( 2-methyl-6-butylphenol) (M.P. 123 4C) was 2 isolated, the yield being 25 percent).

We claim:

1. A process for preparing a 4,4-monoor poly-thiobis(2,6-tert-butylphenol) having the general formula:

t-butyl t-butyl t-butyl 0 nol.

5. The process of claim 1, wherein the solvent is propanol. 

2. The process of claim 1, wherein the hydroxide is potassium hydroxide.
 3. The process of claim 1, wherein the solvent is methanol.
 4. The process of claim 1, wherein the solvent is ethanol.
 5. The process of claim 1, wherein the solvent is propanol. 